feature request: support adding node with xml file

[Khai Do]

This is a feature request. It would be nice if python-jenkins create_node() method could read an xml config containing the node info and create the node from the xml data. That's how create_job() method works so would be great if there was an equivalent for create_node()

Example:

NODE_CONFIG_XML = '''<?xml version="1.0" encoding="UTF-8"?>
<slave>
  <name>slave1</name>
  <description>This is my test slave</description>
  <remoteFS>/home/juser</remoteFS>
  <numExecutors>2</numExecutors>
  <mode>NORMAL</mode>
  <retentionStrategy class="hudson.slaves.RetentionStrategy$Always"/>
  <launcher class="hudson.plugins.sshslaves.SSHLauncher">
    <host>slave1.jenkins.org</host>
    <port>22</port>
    <credentialsId>10f3a3ce-b5b5-4279-b60b-43b5bdb0e46a</credentialsId>
  </launcher>
  <label>precide py27</label>
  <nodeProperties/>
  <userId>anonymous</userId>
</slave>'''

method invocation:
create_node('slave1', NODE_CONFIG_XML)